Railroad crossing construction

ABSTRACT

A railroad crossing construction. The construction includes the conventional rails and ties. In addition there are provided a plurality of flat traffic plates which may be steel or other appropriate material. Each plate is positioned substantially horizontally so as to provide a flat surface for automobile traffic. Crosswise of the rails in one embodiment there are four main plates and two auxiliary plates. Each of the main plates has a downwardly extending flange on the sides of the plates which are parallel to the rails. Two of the main plates extend inwardly from each associated rail and their downwardly extending inner flanges rest on associated ties at approximately the central portion of the tie. The said inner flanges are secured to each other but are insulated from each other against the passage of electricity. Each of these plates contacts one of the rails at the adjacent end and rests on the flanges of the rail. On the opposite side of each rail is a similar plate which extends outwardly and has its downwardly extending flange secured to the outer end of the associated tie. Pivoted to each of these outwardly extending plates is a hinged plate which normally rests upon a fixed support adjacent the sides of the right of way. Should the rails, ties and ballast be forced downward by the weight of the train, truck or other vehicle passing over the crossing or should the crossing settle by reason of time or weather, the hinged outer plates pivot to accommodate for the movement of the rails and ties.

U ilmte States Patent 1191 1111 3,861,591 Rector Jan. 21, 1975 RAILROADCROS SINGCONSTRUCTION Each plate is positioned substantiallyhorizontally so [76] Inventor: Roger R Rector 1720 Birchcrest as toprovide a flat surface for automobile traffic. Rd. Columbus Ohio 43221Crosswise of the rails in one embodiment there are four main plates andtwo auxiliary plates. Each of the Filedi y 1973 main plates has adownwardly extending flange on the sides of the plates which areparallel to the rails. Two [211 App! L972 of the main plates extendinwardly-from each associated rail and their downwardly extending innerflanges [52] US. Cl. 238/8 rest on associated ties at approximately thecentral [51] Int. Cl. E016 9/02 portion of the tie. The said innerflanges are secured [58] Field of Search 238/8, 2, l, 7, 9 to each otherbut are insulated from each other against the passage of electricity.Each of these plates References Cited 7 contacts one of the rails at theadjacent end and rests UNITED STATES PATENTS on the flanges of the rail.On the opposite side of each 1,493,406 5/1924 Van Doren et al. 238/8rail is Similar Plate which extends outwardly and has 1,565,787 12/1925B11110 238/8 its downwardly extending flange Secured t Outer 1 3 5 24411/1932 di et l 233/9 end of the associated tie. Pivoted to eachof theseout- 2,471,167 5/1949 Oxenr iderm; 238/8 wardly extending plates is ahinged plate which nor- Primary ExaminerM. Henson Wood, Jr. AssistantExaminer-Richard A. Bertsch [57] ABSTRACT A railroad crossingconstruction. The construction includes the conventional rails and,ties. In addition there are provided a plurality of flat traffic plateswhich may be steel or other appropriate material.

41 4s 36 66 23 e1 '31 t mally rests upon a fixed support adjacent thesides of the right of way. Should the rails, ties and ballast be forceddownward by the weight of the train, truck or other vehicle passing overthe crossing or should the crossing settle by reason of time or weather,the hinged outer plates pivot to accommodate for the movement of therails and ties.

9 Claims, 5 Drawing Figures 51 v 55 71 64 56 s 52 67 g; 1'

75 77 21 77a. 19 11 7a 22 78a 75 1 1.

RAILROAD CROSSING CONSTRUCTION BACKGROUND OF THE INVENTION 1. Field ofthe Invention Much difficulty at railroad crossings has been encountereddue to the movement up and down of railroad tracks because of the weightof trains and other vehicles passing over the tracks, especially at therailroad crossings. The problem of replacing heavily travelled gradecrossings is difficult, and the expense and inconvenience of replacingsuch crossings is considerable. As a crossing settles due to heavytraffic, the crossing becomes rough and vehicles going over the roughcrossings are damaged and often loads are partially dumped at suchtimes. The cost of maintenance of such crossings also has been quitehigh. It is reported that at one crossing at the Baltimore works of theWestern Electric Company, equipment suffered mechanical damage, tiresblew out on vehicles, and reels of wire were dumped from their carriersbecause of such damage to the crossing. Traditionally, grade crossingsare a challenge to the ingenuity of engineers and the nightmare ofmaintenance departments, charged with the responsibility of installingand maintaining them. Crossing damages cost individuals and plantsthousands of dollars a year. Many attempts have been made to solve thisproblem but no attempt has solved it to the satisfaction of the public,the users, the plant owners, the railroads and others.

2. Description of the Prior Art Some of these attempts to solve thisproblem have been patented. The four Muchnic U.S. Pat. Nos.1,154,534,1,551,165,1,725,410 and 1,725,411, show intermediate platesbetween the two rails which rest upon the flanges of the rails andmainly show approach plates which rest partly on the rail flanges andpartly on the concrete roadway at either side of the track. Many otherpatents disclose metallic plates interposed between the rails of thetrack and the opposite sides of the right of way at a railroad crossing.Such plates are also disclosed in Jensen U.S. Pat. No. 1,557,950,reissue No. 17,201, Pearson et al. U.S. Pat. No. 1,710,030, MulvihillU.S. Pat. Nos. 1,691,078 and 1,743,829, Dailey et al. U.S. Pat. No.1,758,935, Myers U.S. Pat. No. 1,827,823, Ferneding et al. U.S. Pat. No.1,885,244, Greely U.S. Pat. No. 2,076,338 and Oxenrider U.S. Pat. No.2,471,167.

Many of the patentee inventors recognize the problem which has beenstated substantially as follows:

Track rails and railroad beds tip, rise, and fall due to weather andtraffic. It is therefore very difficult to keep railway and highwayjunctions in such condition as to provide a level crossing surface forlong periods of time. It is, of course, very desirable that the platesintermediate the rails and on the sides remain even with the top of therails. Otherwise excessive wear and damage are caused to engines, trainsand other vehicles travelling over the crossing. This flush or evensurface is lost often shortly after the construction of a crossing. Thecrossing becomes rough and uneven because of shifting of the track railsor settling of the road bed. Heavy cargo carrying road vehicles may alsocause crossings to become rough and uneven. Continued maintenanceservice is thus required. This causes great expense to railroad andhighway authorities.

Attempts to relieve these difficulties and expense have been attemptedby providing surfaces which are directly supported on the track railsand are thus free to move up and down with changes in the road bed.These types of crossings are generally of metal construction andalthough they contract and expand with changes in temperature, they arerelatively inflexible and not only tend to buckle upon expansion andloosen upon contraction, but also fail to maintain proper alignment withthe sides of the roadway.

None of the prior art patents appear to have any sug gestion of a hingedstructure excepting only the Pearson et al. U.S. Pat No. 1,710,030. Thepivot in the center of the tracks shown in this patent does not solvethe problem. It was apparently only provided for ease of installation.In my construction the whole inner construction of the crossing isallowed to float as it were, and the hinge action at the outer edgesretains substantially perfect alignment with the roadway regardless ofage, track conditions or vehicle road conditions. It permits normalvertical changes of level due to passing locomotives and rail cars. Itprevents damage to locomotives and rail cars and lading due to bouncingover solid type crossings. The crossing construction may easily beremoved for rail or tie replacement or inspection and replaced withoutdamage. It may even be removed and installed at a different location. Itis constructed in interlocking sections and thus provides for easyhandling, shipping, stowing and is adaptable to any size crossing andeven on ordinary curves. Practically no maintenance is required.

SUMMARY OF THE INVENTION In this invention there is provided a railroadcrossing including a plurality of railroad ties, a pair of rails securedto the ties and a plurality of main inner plates resting partially onthe rails and secured to or resting on the ties. In addition to theplurality of main inner plates there are a pair of auxiliary outerplates pivoted to the main plates and resting upon solid foundations atthe sides of the right of way.

My railroad crossing construction comprises a plurality of railroadties, a pair of rails secured to said ties, a pair of main plates foreach rail, each such plate contacting one of said rails on one side ofthe rail, resting on the flange of the rail, and extending away from therail in a direction opposite to the other plate so that there is aninwardly extending main plate and an outwardly extending main plate,having in the preferred embodiment, means for securing the outer portionof each of said outwardly extending plates to the outer portion of someor all of the associated ties, together in combination with an outwardlyextending auxiliary plate hingedly connected to an outer portion of eachof the outwardly extending main plates and resting upon a support at itsouter end slidingly so that the ties, rails, main plates may tip, ormove up and down while at the same time the outer portions (theauxiliary plates) lead smoothly from the roadway to the main plateswhich are flush with the rails and are secured to the ties, and can moveup and down with the floating of the tie and rail construction.

One of the objects of this invention is to provide a railway crossingconstruction.

Another object is to provide a railway crossing structure which iseconomical in installation and maintenance and is efficient.

A further object of the invention is to provide a safe, smootheconomical railroad crossing for rail and vehicular traffic.

A further object of the invention is to obtain a smooth railroadcrossing in which the hinge action retains reasonable alignmentregardless of age, track condition, or vehicle road condition andpermits normal vertical changes of level of the rails due to highwaytrucks passing over the crossing or due to passing locomotive and railcars, and in which damage to locomotives and rail cars and lading and tohighway vehicles due to bouncing over solid type crossings is minimizedor prevented.

A further object of the invention is to provide an economical railroadcrossing which can be installed in hours instead of days and with a muchsmaller crew, which may be removed for rail or tie replacement orinspection and replaced without damage, which may be removed andinstalled at another location, and which is constructed withinterlocking sections and provides for easy handling, shipping, stowingand is adaptable to any size crossing even on ordinary curves.

A further object of the invention is improvement in public relations byeliminating damage to highway vehicles, their occupants and ladings ofcitizens who drive over a railroad crossing inasmuch as the averagepublic contact with a railroad now (since curtailment of passengertrains) is at a grade crossing.

Further objects of the invention are to provide a railroad crossingwhich stays in perfect alignment with the track, requires practically nomaintenance, has excellent drainage and wherein the rail or tieinspection is easy and the spikes are locked in place.

I have found that the above and other objects of the invention can beattained by a railroad crossing construction comprising a plurality ofrailroad ties, a pair of rails secured to said ties, a pair of mainplates for each such rail, each such plate contacting its associatedrail on the side of said rail opposite to the other associated plate andeach such plate extending away from said rail in a direction opposite tothe other associated plate so that there is for each rail an inwardlyextending main plate and an outwardly extending main plate together withmeans for securing the inwardly extending plates to each other adjacentto the center of the ties and with means for securing the outwardlyextending portion of each said main outwardly extending plate to anouter portion of some of the ties and in combination a pair of outwardlyextending auxiliary plates hingedly connected to the outer portion ofeach of the outwardly extending plates and a support for the outer endsof said auxiliary plates,

BRIEF DESCRIPTION OF THE DRAWINGS In order that my invention may be morefully disclosed, reference is had to the accompanying drawings whichillustrate forms of apparatus embodying the foregoing and such otherprinciples, advantages or capabilities as may be pointed out herein oras are inherent in the invention. For purposes of clarity andexplanation, the following description is explicit and the accompanyingdrawings are detailed but it is to be distinctly understood that suchexposition is illustrative only and that my invention is not restrictedto the particular details recited in the specification or shown in thedrawings wherein:

FIG. 1 is a view in section of a preferred embodiment of a railwaycrossing, constructed according to my invention, the section being takenlaterally through the rails and longitudinally of the ties;

FIG. 2 is a fragmentary view in section of one side of an alternativeembodiment ofthe crossing showing supports consisting of shortened outerplates or brackets which do not rest on the ties and showing theposition of the hinged plate as the construction is installed with themain plates and the auxiliary hinged plates horizontal and in alignmentwith each other as they are shown in FIG. 1;

FIG. 3 is a fragmentary view of one side of the construction of FIG. 1but showing the position of the hinged auxiliary plate relative to themain plates when the rails, ties and main plates have been lowered dueeither to settling over a long period of time or due to pressure fromthe top for a short period when heavy train or other vehicle is passingover the rails or the crossing;

FIG. 4 is a view similar to FIG. 3 showing the alignment of the mainplate with the auxiliary hinged plate at a time when the ties, rails andmain plates have been raised from any cause including have been raisedby the supply of additional ballast; and

FIG. 5 is a view in plan of a crossing looking down on the structuresshown in FIG. 1 wherein a portion of some of the plates have beenremoved in order to show the construction below the plates.

DETAILED DESCRIPTION A PREFERRED EMBODIMENT OF THE INVENTION Referringnow especially to FIGS. 1 and 5 of the drawings for a more detaileddescription of embodiment illustrated, it may be seen that I have showna plurality of railroad ties such as 11, l2, l3 and 14, which may restupon ballast 19 which is usually placed upon and covers the earth of theright of way at the highway crossing and elsewhere (or such ties mayeven at times rest directly on the earth). Tie plates such as 21 and 22are secured to the ties as for example, to the tie II as shown inFIG. 1. Resting upon such tie plates 21 and 22 respectively are a pairof railroad rails 23 and 24. Supported partially by the rails 23 and 24and partially by the ties such as ties l1, l2, 13, 14, etc. are aplurality of main inner traffic plates such as 31, 32, 33, 34 and 35 anda plurality of main outer traffic plates such as 36, 37, 38 and 39, etc.Hinged to the main outer plates are a plurality of hinged auxiliarytraffic plates such as 41, 42, 43, 44 and 45, etc. such hinged auxiliaryplates being pivoted on pins such as 48 and 49 which extend throughbores such as 51 and 52 through the outer main plates and through thehinged plates.

Each of the rails have base flanges such as S5 and 56 and each of themain traffic plates have a pair of downwardly extending flanges whichrest either on one of the rail flanges or on one or more of the ties.Thus for example, in FIG. 1 the main inner traffic plate 31 has flanges61 and 62. The flange 61 is shaped so that its outer end nests in theportion of the rail 23 between the rail base flange 55 and the upperbearing surface of the rail and thus contacts the narrow verticalportion of the rail. The extreme outer end of the flange 61 rests uponthe base flange 55 of the rail 23. The flange 62 is shaped somewhat likea reversed L and has its lower portion resting upon the tie 11.Similarly the main inner traffic plate 32 has a flange 63 substantiallyidentical with (but reversed as to) the flange 61. It also has a flange64 which is substantially identical with the flange 62 but is reversedrelative thereto. The main outer traffic plate 36 has a flange 65 whichis also substantially reversed L-shaped and extends downward from thepivot point about pin 48 and at its lower end rests upon the outer endof the tie 11. At its inner end the traffic plate 36 has a flange 66somewhat like the flange 61 but having a T-shaped portion which extendsinto the space between the rail base flange 55 and the rail head of rail23. The main outer traffic'plate 37 has a flange 67 correspondingsubstantially to the flange 65 but reversed relative thereto and a.flange 68 corresponding substantially to the flange .66 but reversedrelative thereto. The flanges 62 and 64 have an insulation strip 69interposed between them, such strip being a nonconductor of electricity;A bolt 71 passing through the flanges 62 and 64 and through theinsulation strip 69 secures the two flanges and the insulation striptogether. The bolt itself may be made of, a material which is anon-conductor of electricity or may be a metal bolt with an insulatingbushing which is a non-conductor of electricity and thus the trafficplates 31 and 32 are insulated electrically from each other in the usualmanner.

Spikes such as 75 and 76 secure the flanges 65 and .67 to the tie 11 atpoints near the outer end of the tie and spikes such as 77, 77a, 78, and78a secure the tie plates 21 and 22 to the tieat points inward from thespikes 75 and 76. Flanges 62 and 64 may be secured by spikes to the-tie11 if desired. Many if not all of the spikes (e.g., see spike 78) securenot only the associated tie plate but also the rail itself to some ofthe ties. The outer ends of the pivoted plates 41 and 42 rest upon slabs81 and 82 whichmay be of concrete or any other suitable material. Theslabs may extend all of the way across the roadway or each may beshorter (each extending part of the way across) and there may be severalso that they in effect extend all of the way across. The roadway outsideof the railroad right of way is indicated by numerals 83 and 84.

In FIG. 1 the pivoted traffic plates such as 41 and 42 are shown in anormal position they might assume when the structure is installed. Itwill be noticed that the pivoted traffic plate 42 is in substantialhorizontal alignment with the main traffic plates 31, 32, 36 and 37 andalso with the pivoted traffic plate 41. However, should either the earthor the ballast of the foundation or the ties sink for any reason to aposition such as is shown in FIG. 3, the auxiliary traffic plate 42 willpivot about the pin 49 (or auxiliary traffic plate 41 about pin 48).Then though the auxiliary plate 42 will not be in exact alignment withmain traffic plates 31, 32, 36 and 37 nor in exact alignment with theauxiliary traffic plate 41, its

angle relative thereto will be slight and a road vehicle passing alongthe roadway, across the railroad will not encounter the shocks now sooften received at such crossings. On the other hand should the earth orthe ballast be raised for any reason and should the ties such as 11 beraised, the auxiliary traffic plate 42 will again pivot about the pivotpin 49 as shown in FIG. 4. Then although the hinged traffic plate 42will not be exactly in line with the plates 31, 32 and 41, the anglewill not be great and vehicles passing along the roadway crossing therails will not feel appreciably jarred due to the raising of the railsand/or of the construction supporting the rails. i

In FIG. 2, there is shown an alternative construction. Therein the rail124 is supported'by tie plate 122 which is in turn supported by tie 111and ballast 119. The inner main traffic plate l32'nests between the baseflange and head of rail 124, and-rests at one end on the base flange ofrail 124. At its opposite end, the construction of main flange isidentical with inner main traffic plate 32. However, the support 137differs from main outer traffic plate 37 in that it has no outer flangebearing on the tie 111. The auxiliary traffic plate 142 is pivoted on apivot bolt 149 which extends through inasmuch as the structure mayobviously be duplicated for each pair of rails.

[t is to be understood thatthe above described embodiments .of myinvention are for purposes of illustration only and that various changesmay be made therein without departing: from the spirit and scope of theinvention as defined in the following claims.

I claim:

1.. A railroadcrossing construction comprising:

a plurality of railroad ties;

a pair of rails secured to said ties;

a main traffic plate for each rail, such plate contacting one of saidrails on one side of the rail and resting on the flange of said rail andextending away fromsuch rail in a direction toward the other rail sothat there is an inwardly extending main plate;

an outwardly extending support for each rail;

an outwardly extending auxiliary hinged plate pivotally connected to aportion of each of the outwardly extending supports; and

roadway supports for the outer ends of said outwardly extendingauxiliary plates in which each outwardly extending support is anoutwardly extending main traffic plate;

in which there is also provided means for securing the outer portion ofeach of said outwardly extending main traffic plates to an outer portionof one of the associated ties; 1

in which each of the main traffic plates is formed with a downwardlyextending flange at each end;

in which the two inner flanges of the two inwardly extending plates areseparated from each other by a spacing strip which is not a conductor ofelectricity; and I in which theflanges at the outer ends of theoutwardlyextending main traffic plates are secured to the outer end ofthe associated tie by a railroad spike.

2. A railroad crossing construction comprising:

a plurality of railroad ties;

a pair of rails secured to said ties;

a plurality of pairs of main plates for each such rail, each such platecontacting its associated rail on the side of said rail oppositeto theother associated plate and each such plate extending away from said railin a direction opposite to the other associated plate so that there isfor each rail a plurality of inwardly extending main plates and aplurality of outwardly extending main plates;

means for securing the inwardly extending plates to each other adjacentto the center of the associated ties;

means for securing the outwardly extending portion of each of saidmainoutwardly extending plates to an outer portion of the associated ties;

a pair of outwardly extending hinged auxiliary plates pivotallyconnected to an outer portion of each of the outwardly extending plates;and

roadway supports for the outer ends of said auxiliary plates.

3. The structure of claim 2,

in which the ties are supported by the earth and by ballast but are freeto rise and fall with passage of engines and cars.

4. The structure of claim 3,

in which the outer ends of the outwardly extending main plates, as wellas each of the rails are secured to the ties by spikes.

5. The structure of claim 4,

in which the outer ends of the auxiliary hinged plates are supported bysupports associated with the highway.

6. The structure of claim 2,

in which the surface of the crossing and track, including the ties,rails, and plates may move up and down if the earth or the ballast israised or settles.

7. The structure of claim 2,

in which each of the main plates is provided at each of its ends with adownwardly extending flange.

8. A railroad crossing comprising:

a plurality of railroad ties;

a pair of rails secured to said ties;

a plurality of pairs of main plates for each such rail,

each such plate contacting its associated rail on the side of said railopposite to the other associated plate and each such plate extendingaway from said rail in a direction opposite to the other associatedplate so that there is for each rail a plurality of inwardly extendingmain plates and a plurality of outwardly extending main plates;

means for securing the inwardly extending plates to each other adjacentto the center of the associated ties;

means for securing the outwardly extending portion of each of said mainoutwardly extending plates to an outer portion of the associated ties;

a pair of outwardly extending hinged auxiliary plates pivotallyconnected to an outer portion of each of the outwardly extending plates;and

roadway supports for the outer ends of said auxiliary plates;

in which each of the main plates is provided at each of its ends with adownwardly extending flange;

in which each rail is clamped between the downwardly extending flangesof the two main plates associated therewith and in which the flanges atthe inner end of the two inwardly extending plates are secured to eachother adjacent the center of the tie by bolts extending through thedownwardly extending flanges of said inwardly extending plates andthrough a resilient packing interposed between said flanges of saidinwardly extending main plates.

9. The structure of claim 8,

in which the packing is of a material which is a nonconductor ofelectricity.

1. A railroad crossing construction comprising: a plurality of railroadties; a pair of rails secured to said ties; a main traffic plate foreach rail, such plate contacting one of said rails on one side of therail and resting on the flange of said rail and extending away from suchrail in a direction toward the other rail so that there is an inwardlyextending main plate; an outwardly extending support for each rail; anoutwardly extending auxiliary hinged plate pivotally connected to aportion of each of the outwardly extending supports; and roadwaysupports for the outer ends of said outwardly extending auxiliary platesin which each outwardly extending support is an outwardly extending maintraffic plate; in which there is also provided means for securing theouter portion of each of said outwardly extending main traffic plates toan outer portion of one of the associated ties; in which each of themain traffic plates is formed with a downwardly extending flange at eachend; in which the two inner flanges of the two inwardly extending platesare separated from each other by a spacing strip which is not aconductor of electricity; and in which the flanges at the outer ends ofthe outwardly extending main traffic plates are secured to the outer endof the associated tie by a railroad spike.
 2. A railroad crossingconstruction comprising: a plurality of railroad ties; a pair of railssecured to said ties; a plurality of pairs of main plates for each suchrail, each such plate contacting its associated rail on the side of saidrail opposite to the other associated plate and each such plateextending away from said rail in a direction opposite to the otherassociated plate so that there is for each rail a plurality of inwardlyextending main plates and a plurality of outwardly extending mainplates; means for securing the inwardly extending plates to each otheradjacent to the center of the associated ties; means for securing theoutwardly extending portion of each of said main outwardly extendingplates to an outer portion of the associated ties; a pair of outwardlyextending hinged auxiliary plates pivotally connected to an outerportion of each of the outwardly extending plates; and roadway supportsfor the outer ends of said auxiliary plates.
 3. The structure of claim2, in which the ties are supported by the earth and by ballast but arefree to rise and fall with passage of engines and cars.
 4. The structureof claim 3, in which the outer ends of the outwardly extending mainplates, as well as each of the rails are secured to the ties by spikes.5. The structure of claim 4, in which the outer ends of the auxiliaryhinged plates are supported by supports associated with the highway. 6.The structure of claim 2, in which the surface of the crossing andtrack, including the ties, rails, and plates may move up and down if theearth or the ballast is raised or settles.
 7. The structure of claim 2,in which each of the main plates is provided at each of its ends with adownwardly extending flange.
 8. A railroad crossing comprising: aplurality of railroad ties; a pair of rails secured to said ties; aplurality of pairs of main plates for each such rail, each such platecontacting its associated rail on the side of said rail opposite to theother associated plate and each such plate extending away from said railin a direction opposite To the other associated plate so that there isfor each rail a plurality of inwardly extending main plates and aplurality of outwardly extending main plates; means for securing theinwardly extending plates to each other adjacent to the center of theassociated ties; means for securing the outwardly extending portion ofeach of said main outwardly extending plates to an outer portion of theassociated ties; a pair of outwardly extending hinged auxiliary platespivotally connected to an outer portion of each of the outwardlyextending plates; and roadway supports for the outer ends of saidauxiliary plates; in which each of the main plates is provided at eachof its ends with a downwardly extending flange; in which each rail isclamped between the downwardly extending flanges of the two main platesassociated therewith and in which the flanges at the inner end of thetwo inwardly extending plates are secured to each other adjacent thecenter of the tie by bolts extending through the downwardly extendingflanges of said inwardly extending plates and through a resilientpacking interposed between said flanges of said inwardly extending mainplates.
 9. The structure of claim 8, in which the packing is of amaterial which is a non-conductor of electricity.